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Safety Section

This section will provide information that applies to the safe operation of most motorgliders, rather than type-specific advice. Most articles will begin life as an ASA newsletter article, but here it can be more easily accessed and kept up-to-date than is possible using the newsletter and the archives. Significant changes to website articles will be announced in the newsletter and in the "News" section of the web site.

If you have suggestions for web site articles, or want to suggest additions or changes to current articles, please post a suggestion on the ASA newsgroup, or contact any of the ASA directors.Operating a self-launching sailplane

The Warnings – Read this first!

Any combination of tow vehicle and trailer will be safe if you go slow
enough. What people really mean when they say "it's unstable", is "it's
unstable at the speeds I want to tow".

The problem is we don't have a good way of determining how safe
(stable) the combination is at a given speed. By “good”, I mean a
reliable, simple way to determine the safety margin for you driving
your vehicle while towing your trailer. As you know, people sometimes
do determine what is definitely too fast by crashing, or, if they are
lucky, just scaring themselves silly. Vehicle engineers can make
measurements, calculations, and tests that would determine the
safety/speed tradeoffs, but we don't have access to that expertise.

What we have in this section is some generic advice and specific owner
experiences. Because there are so many variables, you should not
automatically assume that what works well/poorly for one person will
work just as well/poorly for you. For example, two cars of the the same
make, model, and year can come with different tires, wheels, and
suspensions, depending on the exact “package” of options purchased with
them. This can produce substantial differences in their towing
stability.

Some rules to live by (this is not a complete set):

If the trailer is constantly wiggling, you may be going too fast. Slow down.

If you feel you might be going too fast, you are going too fast. Slow down.

If your wife or other people are too frightened to ride with you, you are going way too fast. Slow way down.

Improving towing stability

The simplest technique is “slow down”. The slower you go, the steadier the tow vehicle and trailer will be. It works.

Next, check your tire pressure in the tow vehicle and the trailer.
Running the pressures 5 psi above normal might make a noticeable
difference. Check the tires every day you travel by at least looking at the tires for one that looks softer than the others.

Ensure you have between 5% and 10% of the trailer weight on the tongue.
Shift some of the items you carry (wing dollies, gas cans, tool boxes,
etc.) to do this.

And now, the methods that aren't so easy. Some choices have to be made
when you select the vehicle or trailer; some can be made to the one you
already own.

Selecting a new tow vehicle

There are some design features that make for a better tow vehicle, in rough order of importance:

The distance from rear axle to tow ball: shorter is better

Wheel base: longer is better

CG: lower is better (a mini-van versus a SUV, for example)

Weight: heavier is generally better.

Some of the newest vehicles have active stability control that
may improve towing stability, but I have no idea how much these systems
can help us. We are eager to hear reports about these systems, so
please report your experience with them to the group!

The last section (Vehicle Experiences) lists vehicles that other owners have used and how well they worked out for them.

Improving your current tow vehicle

Note: before changing tire
types or sizes, check your manual (or with the manufacturer) carefully,
as tire choice can affect the safety of some SUVs and other higher CG
vehicles by increasing roll-over risk, and perhaps other problems.

The easiest change is better tires. A higher speed rating than the
original tires will usually improve the stability, and the higher the
better. The ride might not be as smooth.

Next easiest is a “wheel upgrade” to a bigger diameter, ; e.g., from a
15” to 16” (or even a 17”). You'll need new tires of the same outside
diameter for the new wheels. That gives you a lower profile tire
(sidewall height to tire width), which reduces the tread deflection
under side loads (cornering or while “swaying”). The ride will
definitely not be as smooth with these lower profile tires, except on
good highways. Going to a higher speed rating than the original tires
will help, too.

Make sure the new wheels and tires are compatible with the vehicle and
won't cause suspension interference when turning or driving over bumps.
The wheel/tire/car dealer should be able to tell you this. A “return if
they don't fit” agreement is a good idea.

If you still aren't happy with the tow vehicle, it might be possible to
improve it with better shocks, bigger sway bars, or wider wheels.
Because it's hard to predict the effects of these changes or to test
their benefit easily, you are on your own.

Selecting a more stable trailer

Getting two axles instead of
one will give a much more stable trailer. The biggest reason not to get
the two axles is the extra difficulty of moving the loaded trailer
around by hand. An empty two axle trailer is generally manageable by
one person on level ground, but with the glider in it, you'll likely
need help or a vehicle to do more than rolling it back and forth with
small changes in direction. If you need to turn it 180 degrees in a
small area, as I do, you're going to need some more muscle, either on
you or in the form of a helpful neighbor!

While the comments above may reflect the majority opinion, not everyone
agrees the two axle trailer is that much trouble. Here are some
opinions on single versus dual axles:

John Murray (USA Schleicher dealer), Aug. 2007:

John used to agree with Uli [Kremer] at the factory that a single axle
is fine, but then “sort of changed my thinking as the ship's value has
climbed so much. You have $200K in the box and no one denies that the
two axle system is more stable and definitely better in a blow out. I
have moved softly to the tandem axle column even though Uli at AS and
Alfred [Spindleberger] at Cobra prefer single axles. To me, $200K is a
lot of money! You can quote me.”

Russ Owens, Aug. 2007:

“I carefully researched the possibility
of ordering a double axle trailer to replace the single axle trailer
that I destroyed in the towing accident. Several major factors came
into play in deciding against ordering a double axle trailer. All the
experienced people I consulted seemed to agree that a double axle
trailer is much more difficult or impossible to maneuver when
disconnected from the tow vehicle. Since I must maneuver the loaded
trailer manually to park it at the side of my house, that was a major
factor in my decision to go with a replacement single axle trailer.”

Mitch Polinsky, March 2009:

“I have a two axle Cobra trailer and am very happy with it; not as hard to move around as some suggested, and very stable.”

Improving your current trailer

Remember, these are suggestions, not guarantees! While others have had
success with these changes, it's not possible to know in advance how
well they will work for you. It is even possible a change will worsen
your situation, so please be cautious when towing the trailer after any
changes.

Do it with tires and wheels..

The easiest change is better
tires. A higher speed rating than the original tires will usually
improve the stability, and the higher the better.

Next easiest is wheels with a larger diameter, e.g., going from 14” to
15” or 16”, or from 15” to 16” or 17”). That allows using a tire with
lower profile (sidewall height to tire width), which reduces the tread
deflection under side loads (cornering or “swaying”). It's important
the wheels have the correct “offset” (the position of the hub to the
rim), so the wheel bearings are loaded properly and the tire doesn't
rub on the trailer or fender. If you are feeling sporty, you could get
some fancy aluminum wheels.

17" wheel with low profile tire on an ASW 27 Cobra trailer

Get tires of the same outside diameter as the original tires, otherwise
the surge brakes will not operate properly. Might as well go to a
higher speed rating – it helps, and it's usually a cheap upgrade.

Tire choices

Commonly available tire types are P (passenger car), LT (light truck) and ST
(special trailer). While each tire series shares basic construction
methods, the details vary meaningfully among the three.

There are other differences:

P tires use a load rating system that is different from ST and
LT tires; generally, you have to discount their rating 10% to get the
equivalent ST or LT rating.

ST tires speed rating is 65 mph. The speed rating increases to 75
mph IF you increase the tire pressure to 10 psi above the pressure
required for your load at 65 mph. These are not the tires for folks
that like to drive 80 mph across the Nevada highways in 100 deg F
temperatures.

ST tires come in both bias-belted and radial construction. The only advantage to a bias-belted trailer tire is it's cheaper.

LT tires are a bit "stiffer" than either P or ST tires, and are available in speed ratings to at least 118 mph.

Suggestions:

P tires might work fine, but I don't know what speed and load
ratings would ensure this. If I decided to use P tires, I'd use them at
the pressure that gave a load rating of ~40% more load rating than the
load they has to carry. I'd choose a speed rating at least 20 mph
higher than the speed rating on my tow vehicles tires.

If you like the way the trailer tows, staying with the same make
and model of tire means no surprises. The same type and size tire from
an equally trusted manufacturer is probably good, too.

If you like to tow faster than 70, don't use ST tires; instead, get
an LT tire rated at least 20 mph more than your intended tow speed.

Do it with a better hitch connection...

The only “sway
dampener” I know that is directly compatible with our Cobra trailers is
the Alko AKS Stabiliser series, similar to the AKS1300 shown in the
picture. Check with the Cobra factory before ordering one so you get
the correct model number. It works by clamping onto the towball, using
friction to dampen swaying. It replaces the standard coupling on the
trailer tongue, and you have to use the correct 50 mm ball and mount
with it. The ball can not just be bolted on, as it might work loose.

They cost several hundred dollars and might have to be ordered from
England or Europe. The two pilots I know that have used them on their
DG 800's say they work very well. See Jim Herd's article in Aug. 2001
Soaring magazine, or Gary Evans' article in the Aug. 2003 ASA
newsletter (available online from the ASA web site).

Weight distributing hitches compensate for high tongue loads
(relative to your tow vehicle). There are several styles, but only a
few that might work with our “pole” (single tube) trailer tongue AND
with our surge brakes. I don't know anyone using one on a Cobra
trailer, or if they are even available. Start by asking Cobra, then go
from there, and please report any that you find.

Do it with axle relocation...

Moving the axle aft can
markedly improve the trailer stability. For our 34 foot (10.3 meter)
long trailers, a reasonable amount would be about 10” (25 cm). This
will increase the tongue weight about 100 pounds (45 kg), so your tow
vehicle and hitch must be able to handle the increased load.

Several things must be changed to accomplish the axle relocation:

New bolt locations for the axle mounts and the shock absorbers.

The axle mount to tongue mount straps should (probably) be lengthened.

The brake actuation rod must be lengthened.

I know people that did this to Cobra trailers with good results, but no one that's tried it on an ASH 26 E trailer.

Do it by retrofitting dual axles...

I have no idea how practical this is, but it should be a lot cheaper than buying a new trailer!

Other Safety Issues and Mitigation

There are other issues besides stability.

The tongue can crack and break off

Whether you are using chains or not, I think every tongue should be inspected for cracks at
least every year. The most likely place these begin is at a weld on the
tongue, e.g., where the parking brake bracket is welded to the tongue. I inspect the tongue at least once a year.

The trailer can disconnect while traveling

The trailer can disconnect because the coupler wasn't properly
connected in the first place, the tow ball comes loose, the hitch
mounting fails, or the tongue breaks.

If you use safety chains
between the tow vehicle and the trailer (standard operation in the
USA), the chains should be very strong. The trailer can whip violently
if it becomes disconnected from the tow vehicle, so I use two chains
with links of 5/16" (8 mm) thickness.

Trailers, including older Cobra trailers, have had tongues crack (like
mine) and even break off. Safety chains between the tow vehicle and the
tongue don't keep the trailer connected when this happens, so some
pilots continue the chains back to the trailer body, and also make a
sturdy connection there.

The tires can lose air pressure and fail

Most of my
towing is with a motorhome. It's size and weight almost completely mask
what the trailer is doing. Over the 140,000 miles of the towing the
trailer, I've had only one complete tire failure, but I've found two
tires with large bulges in the tread, and one where an edge of the
tread had the steel belt exposed. After the complete failure (blowout) at night on a lonely road in Nevada without cell phone coverage,
I decided I needed to know what the trailer tires were doing way back
there.

The solution was a Tire Pressure Monitoring System (TPMS)
that uses sensors mounted on the two trailer wheels and the six
motorhome wheels, and these send the pressure readings by RF signal to
a dash mounted display. The display allows reading the pressure in each
tire while traveling, plus it automatically warns me if the pressure in
any tire drops by 12%. The pressure reading enables detection of a slow
leak before the pressure gets to the warning stage; the warning gets my
attention if a more rapid loss occurs.

Why a TPMS for the
motorhome? Can't I feel when a tire is going soft? No, not if it's a
rear tire, because it has dual wheels on that axle, and one flat tire
out the four on the axle doesn't seem to affect the handling at all. Of
course, it does overload the tire next to the flat one, since
it now has to carry the full load for that side. Since I'd had four
flats on the motorhome over the years without ever knowing it until I
stopped for some other reason, I decided the motorhome needed the TPMS,
also.

There are several types of systems. I use the PressurePro
system, which mounts a small sensor on each valve stem. It's easy to
do, and the cost is reasonable (about $600 for the display and the 8
sensors in 2007). A similar system is the TST system sold by Camping World and others. It's cheaper at $300 for six sensors (just right for a car and trailer), and the display is easier to mount. I use one on my Camry, and it seems to work fine.

Other types mount inside the wheel like the new
cars, but require dismounting the tires to do it. Prices have come down
since I bought my system.

If you don't have a TPMS, you should check your tires for correct pressure every day before you travel, at least visually, but prererably with a tire gage.

Vehicle Experiences

These
are reports by owners. Again, remember there are many variables in the
towing safety equation, so you should not assume that what works well
for one person will work just as well for you. Not only may other
drivers drive differently than you, but even two cars of the same make,
model, and year can come with different tires, wheels, and suspensions,
depending on the exact “package” of options purchased with them. This
can produce substantial differences in their towing stability.

If you'd like to add your vehicle to the "Vehicle Experiences" list, post the information on the ASA newsgroup or send me (Eric Greenwell) an email. Here's what we need:

the make and model of your tow vehicle

your name

Your glider and type of trailer

the year and options of the tow vehicle, like bigger engine, "towing package", tires
that aren't standard; basically, any changes to the vehicle that might
affect it's towing ability.

how well it towed, what speeds you towed at, how much you've
towed with it, and if there were any changes to your trailer that might
affect how stable it is.

Remember, we're interested in any experiences, good or bad.

BMW X5 SAV

4) My impressions: I've towed this combination about 6000 miles now. This
combination tows extremely well. Completely stable up to the highest speed I've
used (70mph). The car has so much power that performance is good even with the
trailer on. Good rear view: can see back over the trailer top in the rear-view
mirror and around the sides with the wing mirrors. Can nap in the back of the
SUV at rest stops. Good storage area in the front of the trailer. Over long
cruises 19-20 mpg (1 or 2 mpg less than without the trailer). Cobra factory
lighting plug did not initially work properly with US standard trailer socket
supplied by BMW, required rewiring.

Dodge Grand Caravan (mini-van)

Eric Greenwell

1989, 150 hp V6, with towing package

ASH 26 E in a single axle Cobra trailer

I haven't towed the 26 E very much with the Caravan. It did an
excellent job with my 1700 pound trailer for the ASW 20. Towing the 26
E seems stable enough up to 70 mph, but normally I tow at 60-65 because
it's old and the power isn't what it used to be. My trailer has the
1000 kg axle (newer ones have the 1300 kg axle) with Michelin
LT185R14/C, speed rating R.

Ford F-150 Pickup Truck

Mitch Polinsky

2010, 5.0L V8

ASH 26 E in a double axle Cobra trailer

I now use an F-150 pickup truck (crew cab, 6.5 foot bed) as my tow vehicle and as a platform for my pop-up camper that I live in when I go on soaring trips. The camper weighs about 1,050 pounds dry and about 1,200 pounds when I leave on a trip. The F-150 does a great job dealing both with the weight of the camper and pulling the trailer. The whole package is very stable on the highway and I have no sway issues going 75-80 mph. I'm sure this is due in some part to my having a dual axle trailer. My only complaint is that I wish I had more power when climbing hills. Ford came out with a bigger 6.2L V8 engine for the F-150 for 2011 and I would recommend that if one is also carrying a camper in addition to towing. For towing alone, the next engine down the line, a 5.0L V8, would be fine.

Georgie Boy Maverick (motorhome)

The combination is very stable, even at 90 mph while passing other
vehicles, or in strong winds. The motorhome doesn't even know the
trailer is back there, except it's a bit harder to go up hills. 10 mpg
while towing at 60 mph – buying gas isn't for sissies!

GMC Yukon

Russ Owens

Year unknown

ASH 26 E in a single axle Cobra trailer

I have had good success with the Yukon, a gas guzzler

Honda Pilot

Bill Gawthrop

Year unknown

ASH 26 E in a single axle Cobra trailer

I sometime tow my 26E with my Honda Pilot. It does pretty well
below 70 mph, but with occasional oscillations. These don't bother me
very much but my wife will not drive it towing the 26E.

Honda Ridgeline Pickup

Mitch Polinsky

2007

ASH 26 E in a double axle Cobra trailer

When I went looking for a tow vehicle two years ago I thought the
4Runner would be a good choice, but didn't like the way it drove like a
truck. I think the Honda Ridgeline is a terrific vehicle for pulling
the 26E trailer. My only complaint, and it is relatively minor, is that
I can't maintain 60-70 mph going up steep grades. Drops down to 50-55
mph. Other than that, it's terrific. However, I can't assess how much
of the stability is due to the Ridgeline and how much is due to the
fact that I've got a two-axle trailer. I am very happy with my two axle
Cobra trailer. It's not as hard to move around as some suggested, and
it's very stable.

Jon Fitch

Year unknown

ASH 26 E in a single axle Cobra trailer

My Honda Ridgeline does a pretty good job of towing the ASH26. It
is basically the same vehicle as the Pilot, though I think the Pilot
has a shorter wheelbase which would not help. If you are towing over
the Sierra, I think you would find it a bit underpowered - it will
climb the hills but has to work to do it.

Jeep Grand Cherokee

Val Dean

Year unknown

ASH 26 E in a single axle Cobra trailer

I just returned from a 1000 mile trip (Denver to Pinedale, WY)
pulling a single axle Cobra trailer with a Jeep Grand Cherokee. I was
able to maintain 70 - 75 MPH without much ass wagging. I did note that
pulling up hill or level was better than downhill where the ass wagging
sometimes required slowing to 65 mph.

Mike Parker

Years unknown - V6, 4WD with automatic, V8, 4WD with automatic, both had the factory "towing package" option.

ASH 26 E in a single axle Cobra trailer

No problems, both great tow vehicles, normally tow at up to 70 mph
on good roads. I have needed 4 wheel drive to pull a glider (not mine)
out of a field exactly once. So it may not be worth the extra cost and
reduced gas mileage.

Lexus 430 hybrid SUV

Mike Parker

Year unknown

ASH 26 E in a single axle Cobra trailer

No problems. Surprisingly, tows fine uphill in the mountains (I
thought it would be underpowered). Great mileage. I am a little more
careful on winding downhill roads than I was in the Grand Cherokee
because the Lexus feels lighter (and probably is). Because it feels
lighter, I worry about what would happen if I had a panic stop, and
drive accordingly. It is a great tow vehicle overall, however, and I
feel comfortable at 70 mph on good roads.

Subaru Forester

Jim Dingess

2002 with the 2.5 liter engine.

ASH 26 E in a single axle Cobra trailer

The little 4 cylinder engine pulls almost as good as my V8 pickup,
and only slows down on the very steepest hills. The trailer wiggles at
and above 70 mph if not careful with steering, but is fine in all but
the worst winds. When it gets very windy I just slow down, this doesn't
happen very often. 65 mph is very comfortable and is the speed I
usually drive, a little slower in California to avoid a ticket. I get
from 22 to 24 mpg on the highway while towing.

Subaru Outback

Jim Staniforth

2000 with 2.5 liter engine

ASH 26 E in a single axle Cobra trailer

Out of the three vehicles I towed the Nimbus 3 with, the Subaru
blew the doors off the Chevy Tahoe and Holden Commodore. " I always
prefer the metal top Cobra trailer, for bothtowing stability and UV protection."

(comment by Jim Dingess) Staniforth's Outback tows a little better than
the Forester, I retrieved Staniforth (LS-6 at the time) from Eureka,
Nevada with his car, it worked so well, I sold my big Chevy truck and
replaced it with the Forester as it has a little more room than the
outback. The big truck towed better but not enough to justify the extra
fuel burn in my opinion.

Toyota 4Runner

Jim Dingess

year unknown

ASH 26 E in a single axle Cobra trailer

Towed from Williams to Boulder City, Nevada near Las Vegas through
Tehachapi with the 4Runner, it did great. Speeds ranged from 55 to 75
mph. Mostly stayed at 65.

Russ Owens

1998

ASH 26 E in a single axle Cobra trailer

I towed the ASH-26E with it for a while, and wasn't very happy
about the odd dynamics of steering and fishtailing. I lost control at
70 mph of the combination (due to my error in steering) on the way from
San Diego to Ely (aprox. 2003), rolling the 4Runner over and over (8
times?) destroying both the 4Runner and the Cobra trailer containing
the 26E. My wife and I were extremely fortunate to survive the accident
with only minor cuts and bruises. Rex Mayes expertly repaired the minor
damage to the glider. I think the 4Runner was a bit light to be towing
the big trailer, and as I mentioned, the suspension and steering
dynamics of the combination never seemed right to me. It's pretty
obvious (now) that I should have listened to myself and stopped towing
when it just didn't feel right.

Gary Evans

Year unknown

I tow with a Toyota 4-Runner which is a mid sized SUV. While it
would appear to be a good choice for towing I found 60 to be the limit
before sway would start. I believe the problem is that even though it
has fairly heavy suspension you can still induce sideways movement by
pushing with one finger on the rear of the vehicle. After trying every
solution I could think of I finally changed the trailer connector to
Al-Ko AKS 1300 Stabilizer, which works by pad pressure to the ball.
Towing is now stable up to the max speed of the vehicle, which with a 6
cylinder engine and trailer in tow is 85. While pricey at $250 [2003
cost] for the connector and special ball coupler it is cheaper than
unwrapping the car/trailer from a tree.

Ed Salkeld

2003, V8, 2 wheel drive with factory towing package.

I’ve towed about 10-12,000 miles with
it.Tows well up to 70
mph but the not very stable above that.

Toyota Sequoia

Russ Owens

Year unknown

ASH 26 E in a single axle Cobra trailer

I have had good success with the Sequoia, a gas guzzler

Toyota Tacoma Pickup

Hugh Milne

2001 - V6 with the TRD package including the supercharger and free-flow exhaust.

ASH 26 E in a single axle Cobra trailer

The supercharger increases output from about 180 to 245 bhpp, and
means I can pull the 26 over the Sierra Nevada (up from sea level to
over 8,000ft) without ever slowing down, and still get about17 mpg..
(Freeway driving at 55 with no trailer, I get 24 mpg.) It is not a
perfect 26 tow vehicle, it is sensitive to weave if you are not precise
with the steering wheel, but my wife is happy to tow at 75 when we go
across the desert.

Toyota Tundra Pickup

Tom Serkowski

2001 – V6 with manual transmission

ASH 26 E in a single axle Cobra trailer

I tow with a Toyota Tundra pickup and set the cruise control for 78
mph on the freeway ( if the speed limit is 75 :) and have no trouble. I
do slow down a bit for strong cross winds, but have never had the
feeling of imminent loss of control, it just becomes a lot of work
dealing with side gusts.

VW Eurovan

Jon Fitch

Year unknown

ASH 26 E in a single axle Cobra trailer

My VW van was one of the better tow vehicles. 205 hp, very short
coupling between the hitch and axle (like 20 inches or so) - it was
quite stable. Much better than two medium sized SUVs we have owned.